1. Field of the Invention
The present invention generally relates to a composite plated product and a method for producing the same. More specifically, the invention relates to a composite plated product wherein a coating of a composite material containing carbon particles in a silver layer is formed on a substrate and which is used as a material of sliding contact parts such as switches and connectors.
2. Description of the Prior Art
Conventionally, as materials of sliding contact parts such as switches and connectors, there are used silver-plated products wherein a conductive material such as copper or a copper alloy is plated with silver in order to prevent oxidation of the conductive material due to heat in sliding processes.
However, there is a problem in that silver coatings are easily stripped by sliding since they are soft and easily wear and since they generally have a high coefficient of friction. In order to solve this problem, there is proposed a method for electroplating a conductive material with a composite material wherein graphite particles are dispersed in a silver matrix, in order to improve the wear resistance of the conductive material (see, e.g., Japanese Patent Laid-Open No. 9-7445). There is also proposed a method for producing a silver coating, which contains graphite particles, by means of a plating bath to which a wetting agent suitable for the dispersion of graphite particles is added (see, e.g., Japanese Patent Unexamined Publication No. 5-505853 (National Publication of Translated Version of PCT/DE91/00241)). Moreover, there is proposed a method for coating carbon particles with a metal oxide or the like by the sol-gel method to enhance the dispersibility of the carbon particles in a composite plating bath of silver and the carbon particles to increase the quantity of carbon particles in a composite coating (see, e.g., Japanese Patent Laid-Open No. 3-253598).
However, composite plated products produced by the methods disclosed in Japanese Patent Laid-Open No. 9-7445, Japanese Patent Unexamined Publication No. 5-505853 and Japanese Patent Laid-Open No. 3-253598 have a relatively high coefficient of friction and a relatively low wear resistance, so that there is a problem in that the composite plated products can not used as the materials of long-life contacts and terminals. Therefore, it is desired to provide a composite plated product which has a larger content of carbon and a larger quantity of carbon particles on the surface thereof than those of the composite plated products produced by the conventional methods and which has a better wear resistance than that of the composite plated products produced by the conventional methods.